The first chapter serves as the introductory chapter of the book. It sets the stage for the subsequent chapters by providing an overview of the central theme and the research goals of the book. The chapter begins by acknowledging the increasing interconnection between environmental and social issues, making it challenging to distinguish one policy domain from another. Environmental degradation and climate change have far-reaching impacts on social welfare worldwide, while environmental policies aimed at addressing these challenges can have (unintended) social consequences. Similarly, traditional social policies that prioritise economic growth may overlook ecological implications. In response to these interdependencies, the chapter introduces the concept of eco-social policies. Eco-social policies are policies that integrate environmental and social concerns while navigating the tensions between environmental sustainability and social welfare. The primary focus of the book is to evaluate eco-social policies within the context of global governance, with a specific emphasis on two influential international organisations, the OECD and the World Bank. These organisations play essential roles in shaping global policies and have been prescribing environmental and social policy “best practices” for decades. In recent years, they have explicitly recognised the need to link environmental and social policy domains. The chapter also presents the methodical approach and displays how data was collected and analysed while it also outlines the research questions and the structure of the book.